1. Field of the Invention
The present invention relates to an optical link device. More specifically, the present invention relates to an optical link device which performs data communications via an optical fiber by being connected to an optical connector.
2. Description of the Related Art
There are optical devices which perform data communications via an optical fiber by being connected to an optical connector.
An example of a conventional optical link device is described below with reference to FIG. 25.
The optical link device a includes a housing b and a receptacle c connected to the housing b.
The housing b has the shape of a box, the inside of which is formed as an internal space d, and includes an opening on one side.
The receptacle c has the shape of a box with an opening on one side and includes a bottom surface e and a side wall f that stands on the circumferential edge of the bottom surface e. A cylindrical sleeve holder section g, which protrudes in the same direction as the side wall f, is provided on the bottom surface e. The circumferential section of the bottom surface e is attached to the edges of the opening of the housing b, and the internal space d of the housing b is closed by the receptacle c.
A cylindrical sleeve h is fitted inside the sleeve holder section g of the receptacle c. The sleeve h may be formed with materials that allow for high precision machining, such as ceramic or metal materials.
A stopper i, placed in the internal space d of the housing b, is attached to the bottom surface e of the receptacle c. The stopper i is formed in the shape of a cylinder that is short in its axial direction and a center aperture is formed as a light transmissive aperture j. The central axis of the sleeve h attached to the inside of the sleeve holder section g of the receptacle c and the central axis of the light transmissive aperture j are in agreement.
A substantially cylindrical holder ring k is attached to the stopper i. A lens holder 1 is attached to the holder ring k so as to fit therein.
The lens holder 1 may be formed with a metal material and includes a cylinder section m and a closing section n, which closes an opening on one end of the cylindrical section m. A light transmissive aperture o is formed at a center section of the closing section n. The cylinder section m of the lens holder 1 is attached to the holder ring K.
A sealing cap p formed with a metal material is placed inside the lens holder 1.
An optical communications package q includes a device positioning member r, which is called a stem and is formed with a metal material, leads s, one end of each of which is attached to the device positioning member r, and a photoelectric converter (a photo detector or a light emitting device) t. Contact terminals of the photoelectric converter t are connected to the leads.
The photoelectric converter t is sealed in an airtight manner by having the sealing cap p attached to the device positioning member r. One end of the lens holder 1 is attached to the device positioning member r such that the lens holder 1 covers the sealing cap p. By having the photoelectric device t sealed in an airtight manner by the sealing cap p, condensation caused by changes in the surrounding temperature, for example, may be prevented, and the reliability of the operation of the photoelectric device t may be improved.
The sealing cap p and the device positioning member r, as well as the lens holder 1 and the device positioning member r, are joined together through resistance welding in a nitrogen atmosphere.
A spherical condenser lens u is placed between the lens holder 1 and the sealing cap p. The condenser lens u is aligned with the light transmissive aperture o of the lens holder 1.
Part of the leads s of the optical communications package q protrudes outward from the housing b to connect the contact terminals of the photoelectric converter t with a connector of an external device, such as a personal computer.
An optical connector v to be connected to the optical link device a—includes an optical fiber x supported by a connector section w. The optical fiber x has the tip covered by a ferrule y. A biasing spring z is placed between the connector section w and the ferrule y.
The optical connector v is coupled with the receptacle c by having the connector section w fitted therein. At this point, the ferrule y is inserted and fitted inside the sleeve h. The tip surface of the ferrule y inserted into the sleeve h butts against the stopper i. The biasing spring c presses the ferrule y against the stopper i. As the ferrule y butts against the stopper i, the tip of the optical fiber x is aligned with one end of the light transmissive aperture j of the stopper i.
In order to achieve good optical coupling, it is necessary that the positioning of the photoelectric converter t, the condenser lens u and the optical fiber x be adjusted in the optical link device a—in other words, it is necessary that their axes be aligned. This alignment is accomplished by, for example, adjusting the position of the holder ring k with respect to the stopper i on a surface orthogonal to the optical axis, and by adjusting the position of the lens holder 1 with respect to the holder ring k along the optical axis. Once the alignment is completed, the holder ring k is secured to the stopper i, and the lens holder 1 is secured to the holder ring k using, for example, a yttrium aluminum garnet (YAG) laser for instantaneous and firm welding.
When an optical signal is transmitted through the optical fiber x under a condition where the optical connector v is connected to the optical link device a, the transmitted optical signal enters the condenser lens u via the light transmissive aperture j of the stopper i and the light transmissive aperture o of the lens holder 1, and is received by the photoelectric converter (the photo detector) t. The optical signal received by the photoelectric converter t is converted into an electrical signal and is input to an external device through the leads s, thereby performing data transmission.
If, on the other hand, the photoelectric converter t of the optical communications package q is a light emitting device, an electrical signal from an external device is input to the photoelectric converter t via the leads s, is converted into an optical signal by the photoelectric converter t, and is emitted towards the condenser lens u. The optical signal that enters the condenser lens u is input to the optical fiber x via the light transmissive aperture o in the lens holder 1 and the light transmissive aperture j in the stopper i. Data transmission from an external device is thus performed.
The optical link device a described above is designed to either transmit data or receive data. However, there are devices which have both the functions of data transmission and reception as shown in FIG. 26.
This optical link device a′ for both transmission and reception includes a pair of sleeve holders g, g, which are spaced apart from each other, provided in a receptacle c′. Inside the sleeve holders g, g are fitted sleeves h, h, respectively. Stoppers i, i are attached to the receptacle c′ so as to be adjacent to each other, and holder rings k, k are attached to the stoppers i, i, respectively. Lens holder 1, l are attached to the holder rings k, k, respectively. The lens holder 1, l and sealing caps p, p, which are placed inside the lens holder 1, l, are attached to one optical communications package q, which functions as a receiver, and another optical communications package q, which functions as a transmitter, respectively.
The optical communications package q that functions as a receiver includes a photo detector as a photoelectric converter t, and the optical communications package q that functions as a transmitter includes a light emitting device as its photoelectric converter t.
An optical connector v′ to be connected to the optical link device a′ includes optical fibers x, x supported by a connector section w. The tips of the optical fibers x, x are covered by ferrules y, y, respectively. Biasing springs z, z are placed between the connector section w and the respective ferrules y, y.